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Poly(vinyl alcohol) was used to make hydrogels containing various amounts of collagen. These "bioartificial materials", made of synthetic and biological polymers, were studied to investigate the effect of the presence of the collagen on the structural properties of the hydrogels. A comparison between thermal and morphological properties of collagencontaining hydrogels and hydrogels of pure poly(vinyl alcohol) was made.

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The melt mixing of functionalized polyolefins with a surface-modified layered silicate (montmorillonite) was investigated as an approach to prepare the corresponding micro/nanocomposites. The effect of the diethyl succinate groups, derived from the grafting of diethyl maleate (DEM) onto the polyolefins, on compatibility with an inorganic filler and the dispersion in a hydrophobic matrix was extensively investigated. In order to avoid possible interference by polymer multiphase morphology, the amorphous poly(propylene-ran-ethylene) (EPM) (70/30, wt/wt), functionalized with DEM (EPMgraft-DEM), was used in melt mixing with alkyl-ammonium-salt-modified montmorillonite at different weight ratios by using a Brabender mixer. Materials with a nanoscale dispersion of the inorganic phase, as revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, were obtained. Specific interactions, involving the carbonyl groups of the polyolefin functional groups and the polar sites on the filler surface, appeared to assist intercalation and/or exfoliation of the layered system. Similar results were obtained by starting with an unfunctionalized EPM and by performing the grafting reaction with DEM during melt mixing according to a one-step simplified procedure.

Hydrogen outgassing is the most significant factor limiting the attainment of outgassing rates below 10(-12) mbar l s(-1) cm(-2) in stainless steel vacuum systems. This limit turns out to be crucial in very large vacuum systems, like the VIRGO vacuum tubes (2 tubes 1.2 m diam, 3000 m length). Heating the raw material at 400 degrees C in air was suggested as a money saving alternative to the classical vacuum heating at 950 degrees C. We report the results of hydrogen content analysis performed on stainless steel samples submitted to different treatments, and also the measurement performed on a prototype tube (1.2-m-diam, 48-m-long). We concluded that air bake-out drives out most of the hydrogen absorbed in the bulk stainless steel, while the presence of an oxide layer does not reduce the hydrogen outgassing. (C) 1998 American Vacuum Society